A conventional mouse as shown in FIGS. 1 and 2 includes: a ball B rotatably mounted in a mouse box P and protruding downwardly to be rolled on a flat surface from a bottom hole H formed in a bottom portion of the box having an electronic circuit provided in the box, a X-axis encoder E and a Y-axis encoder E' respectively driven by two rollers R1, R2 rotatably contacted with a spherical surface of the ball B, a pressure roller R pressurizing the ball B for ensuring a better contact between the rollers R1, R2 and the ball B, and two detectors D, D' respectively detecting the pulse signals from the two encoders E, E' for electronically sensing the movement pulse signals when moving the mouse either on X or Y axis when rolling the ball B, as processed by the electronic circuit in the mouse box P for producing and transmitting pulse waves to a computer to be decoded and read for moving a cursor on a CRT screen corresponding to the movement of the mouse.
However, such a conventional mouse may have the following drawbacks:
1. For ensuring a well contact between the rollers R1, R2 and the ball B, the spherical surface of the ball such as made of rubber should be frictional to thereby be easily adhered with dusts or dirts when rolled on the flat surface, possibly influencing a smooth rolling operation of the mouse.
2. During a coordinative rolling of the mouse on a flat mat kept on a desk, the mouse may be accidentally moved beyond the scope or area of the flat mat. A returning movement or relocation of the mouse on the mat will interrupt a computer operation, causing inconvenience for the computer operator.
3. The ball B should be touched on a flat surface for its rolling so that the mouse should always be placed on a flat surface, thereby requiring a space for placing the mat and mouse, and also limiting the maneuverability for handling the mouse. For example, the mouse can not be held on an operator's hand by suspending the mouse above a table surface.
4. The computer operator should always by very scrupulous in order to prevent an "escape" of the mouse from the flat mat, thereby reducing the keying efficiency or decreasing the data entry speed to the computer.
The present inventor has found the drawbacks of the conventional mouse, and invented the point-and-draw device of the invention.